Alexandra Black, 22, was passionate about wildlife and had worked just 10 days as in intern at the facility in Burlington, North Carolina.

"The Conservators Center is devastated by the loss of a human life today," it said in a statement.

"While a husbandry team led by a professionally trained animal keeper was carrying out a routine enclosure cleaning, one of the lions somehow left a locked space and entered the space the humans were in and quickly killed one person.

"It is unclear at this time how the lion left the locked enclosure. At no time did the lion ever enter a space that was not enclosed by the park's perimeter fence," the statement added, expressing its condolences to Black's family and announcing it would close temporarily.

The lion was killed so Black could be retrieved, the center said.

Black, a recent graduate of Indiana University, had worked a few weeks at the facility home to dozens of animals and 21 different species, its website says.